The injectors in modern fuel injection systems for internal combustion engines are increasingly controlled by piezoactuators, whose actuating characteristics are more dynamic than those of conventional electromagnetic actuators. The individual piezoactuators are therein controlled according to a pre-specified Start Of Injection (SOI) at a specific trigger time with a specific actuator energy in order to set the desired start of injection. It must be noted in this regard that the transmission of power from the piezoactuator to the injector's valve needle is prone to a delay so that the trigger time of the electric control signal for the piezoactuator and the ensuing start of injection are separated by a delay that is specific to the design type used.
What is problematic therein is that said delay between the trigger time of the electric control signal for the actuator and the ensuing start of injection is subject to fluctuations due to mechanical and electric tolerances, and that can result in errors in setting the start of injection.